Symptoms

Possible cause

Resolution

Contact breaker

Faulty condenser

Replace condenser

points burning

Loose condenser terminal

Tighten terminal screw

Dirty battery terminals

Clean and tighten terminals

Engine revs up but

Clutch slipping

Adjust clutch pressure plate springs.

speed does not

Replace clutch driving plates if friction material

increase or kick

worn

start slips, fails to

Add extra driven plate to increase pressure.

turn engine over

Excessive vibration

Loose or worn engine

Tighten bolts or bush mounting holes to

mountings

remove play

Loose head stabiliser

Tighten bolts

Worn piston and crankshaft

Engine overhaul.

bearings

Worn gearbox main shaft

Gearbox overhaul

bearings

Crankshaft unbalanced

Balance crankshaft.

Blue smoke from

Wet sumping caused by

After standing a few days, check the oil level

exhaust when cold

leaking oil pump valves. Oil

before you start up the engine, if it has dropped

starting

settles in the sump, pushes

or low. Recheck after running for a couple of

past the piston into the

minutes and it should have risen back to

cylinder and burns off as blue

normal. Not a major problem, after periods of

smoke.

standing, turn the engine carefully over on the

kickstart about ten times before you switch on

the fuel and ignition. This will allow the oil pump

to return some of the oil out of the sump

before starting. Alternative fix or replace oil

pump non return valves.

Poor top speed

Retarded ignition

Check and set correctly

performance

Faulty ignition auto advance

Oil advance spindle, check advance springs and

establish functionality.

Dirty or blocked air filter

Clean filter or replace cartridge

Loss of performance

No valve clearance

Adjust tappets correctly

due to poor compression

Burnt valve seats

Replace valve and recut seat

Sticking valve

Clean valve stems and remove gum.

Worn piston rings or bore

Replace rings, re-bore if bore is badly worn.

Piston failure

Usually a holed piston, accompanied by large

amount of smoke from the exhaust caused by

weak mixture.

Engine seizes or becomes

Plug pre-ignition

Fit a cooler plug

tight after prolonged high

Piston seizure

Resolve problem, may require new piston or

speed

caused by incorrect piston

careful smoothing of surfaces.

clearance, weak mixture or

incorrect timing

Mixture weak

Raise needle position, increase main jet or

adjust as per manufacturer instruction.

Oil pressure failure caused

Resolve problem, may require new piston, bore

by lack of oil, oil pump failure

And cams or careful smoothing of surfaces.

Engine knocking when

Ignition too advanced

Retard ignition by a degree or two

accelerating from low revs

Automatic advance/retard

Replace springs

(pinking)

mechanism springs too weak

Engine needs de-coke

Strip top end down and remove carbon from

cylinder head and piston.

Back firing and kicking back

Ignition too advanced

Retard ignition by a degree or two.

Auto-advance unit stuck or

Strip unit and replace any broken parts.

broken spring